The state of a cache may change between the placing of an operation storing data from the cache into the unit pipe or into the store portion of the store and load queue and the completion of the store operation. Store operations are queued to allow the program code to move forward. Because of the nature of store ordering requirements on cache coherency, older operations may modify the validity or location of the cache line within the data cache. These modifications may cause the cache state information which the store operations received upon issue to become old or outdated. Maintaining data integrity requires some mechanism to allow the cache state information for the store operations to be updated.
One way to update transactions is to read the cache state information. It may, however, be desirable to limit access to the cache. For example, a cache may be designed with a single read/write access point, or port. The design may afford simplicity, or be suitable for a smaller or low-power cache. With such a design, to read the cache state information, it is necessary to recycle operations through the unit pipe. Repeated recycling to update the store transaction requires many cycles and blocks other accesses to the cache.
Therefore, there is a need for a method of updating the cache state information for store transactions without reading the cache state information in a manner that addresses at least some of the issues associated with conventional updating of store transactions.